Present-day damping systems in motor vehicles can be subdivided into three groups, namely: passive, semi-active and active damping systems. In all of these damping systems, the magnitude of the damping is dependent upon the relative velocity of the damper. In passive damping systems, the magnitude and the direction of the force, which is applied by the damper, is only dependent upon the relative velocity of the damper. In passive damping systems, a change of the damping force during travel is not provided.
In semi-active damping systems, the damping force can be changed by a change of the fluid or gaseous flow utilizing a valve. In this way, different control programs can adjust the optimal damping force by means of an actuator element in dependence upon the current driving situation. In active damping systems, the desired force in any direction is made available by an actuator independently of the relative velocity of the damper.
A level control system with a control of the vibration dampers of the chassis is known from U.S. Pat. No. 6,164,665. In this system, an actuating signal is used for the control which corresponds to the damping requirement for the movement of the vehicle bodywork. A so-called poor-roadway characteristic value is added to this damping requirement in order to improve the driving safety and comfort. The change of the vibration damping adjustment is determined by the time-dependent trace of the acceleration of the actual spacings of the wheel to the vehicle bodywork. The acceleration is computed by a two-time differentiation of the measured spring displacement.
Furthermore, it is conventional to mount wheel acceleration sensors at respective wheels for determining the relative damping velocity and to undertake the damping control based on the acceleration signals. This method requires a high complexity with respect to the sensors.